A “botnet” is a large number of Internet-connected computing machines/systems that lie in wait for remote commands from one or a few controlling computers. These systems have been compromised and run automated scripts and programs which many times are capable of sending out massive amounts of spam emails, voice-over-internet-protocol (VoIP) messages, and many other types of Internet communications.
One basic characteristic of botnet malicious software is its automated nature. An automated computer program that sends spam messages to many targets could run on a computing machine without the knowledge of the user of the computer machine. The malicious software can function without any input from a user, since the automated nature allows the software to be triggered by packets sent from a malicious remote user (i.e. a hacker) located many miles away.
There are many existing anti-spam technologies such as Internet service provider (ISP) background checks on customers, digital signatures on emails, firewalls, etc. Today, a vast majority of all emails sent worldwide are spam messages, and it is theorized that more than 80% of all the spam messages are generated by botnet machines manipulated by relatively few professional spam gangs.